By far, the hottest eco-spot along the Rio Solimões is the Reserva de Desenvolvimento Sustentável de Mamirauá (Mamirauá Sustainable Development Reserve, tel. 92/3233-9025, www.mamiraua.org.br). The largest protected area of varzéa (Amazonian forest that is seasonally flooded with “white” river water) within Brazil, the reserve is monitored by the Instituto de Desenvolvimento Sustentável de Mamirauá, whose mission is to combine conservation and scientific research with the creation of sustainable employment and lifestyles for local inhabitants.

Apart from traditional fishing and agriculture, an increasing percentage of the local caboclo population work as guides and forest patrollers. Their efforts have not been in vain: The forest is in pristine condition and exploring its jungles, rivers, and lagoons will give you the sensation of having returned to a primordial Eden.

As a result, Mamirauá is one of the best places to see wildlife. Aside from caimans, pink dolphins, sloths, and myriad birds and monkeys, if you’re lucky you might even get to see the very rare scarlet-faced uakari monkey.

Located at the confluence of the Solimões with the Rio Japurá, the reserve is close to the town of Tefé, which also happens to be the last outpost of civilization along the Solimões. To visit the reserve on your own involves a two-day boat trip to Tefé (or a far speedier and more expensive one-hour direct flight from Manaus).